Optical Component Threading Adapters with RMS (0.800"-36) Threads


  • Integrate RMS-Threaded Components with
    Other Industry Standard Threads
  • Adapters Available with Either Internal or External RMS Threads

RMSA6

External RMS Threads
and Internal C-Mount Threads

RMSA1

External M25 x 0.75 Threads
and Internal RMS Threads

M32RMSS

External M32 x 0.75 Threads
and Internal RMS Threads

RMS-Threaded Objective Mounted in Our
30 mm Cage System Using SM1A3 Adapter

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Interactive Selection Guide

RMS-Threaded Optical Component Adapters

This page contains all of our Optical Component Thread Adapters that feature RMS (0.800"-36) threading. Adapters featuring either internal or external threads are available.

For use with microscope objectives, we recommend our brass microscope objective threading adapters. They feature a lip to prevent the microscope objective from being threaded too far onto the mount, and their brass construction is harder than aluminum and less likely to bind to and damage the objective threading.

Our RMS adapters are a subset of our entire line of optical component thread adapters. To view our entire line, please see our Interactive Adapters Selection Guide.

Adapters with External RMS and Internal Industry-Standard Threads
Item # Typical Application External Threads Internal Threads
SM05RMS info Create Objective from SM05 Lens Tube RMS (0.800"-36) SM05 (0.535"-40)
RMSA2
info
Integrate M25 x 0.75 Objective with
RMS Mount
RMS (0.800"-36) M25 x 0.75
RMSA6
info
Integrate Camera Lens to Microscope RMS (0.800"-36) C-Mount (1.00"-32)
SM1A4
info
Create Objective from
SM1 Lens Tube
RMS (0.800"-36) SM1 (1.035"-40)
SM1A4TSa
info
Create Objective from
SM1 Lens Tube
RMS (0.800"-36) SM1 (1.035"-40)
SM1BC
info
Create Objective from
SM1 Lens Tube
RMS (0.800"-36) SM1 (1.035"-40)
RMSW26S
info
Integrate W26 x 0.706 Objective with RMS Mount RMS (0.800"-36) W26 x 0.706b
RMSA4
info
Integrate M27 x 0.75 Objective with RMS Mount RMS (0.800"-36) M27 x 0.75
RMSA10
info
Attach M32 x 0.75 Objective to RMS Mount RMS (0.800"-36) M32 x 0.75
RMSA12
info
Integrate M62 x 0.75 System with RMS Mount RMS (0.800"-36) M62 x 0.75
  • Thermally insulating adapter. See the Thermal Insulation tab above for more information.
  • W26-threaded objectives are sometimes referred to as M26-threaded, but as long as the objective conforms to ISO 9345:2019 or JIS B 7141:2012, it will be compatible with our W26 adapters.
Adapters with Internal RMS and External Industry-Standard Threads
Item # Typical Application External Threads Internal Threads
RMSA1
info
Mount RMS Objective in M25 x 0.75 Mount M25 x 0.75 RMS (0.800"-36)
RMSA5
info
Mount RMS Objective to Camera C-Mount (1.00"-32) RMS (0.800"-36)
SM1A3
info
Mount RMS Objective to SM1 Lens Tube SM1 (1.035"-40) RMS (0.800"-36)
SM1A3TSa
info
Mount RMS Objective to SM1 Lens Tube SM1 (1.035"-40) RMS (0.800"-36)
RMSA7
info
Integrate RMS Objective with M26 x 0.706 Mount M26 x 0.706 (36 TPI) RMS (0.800"-36)
RMSA3
info
Mount RMS Objective in M27 x 0.75 Mount M27 x 0.75 RMS (0.800"-36)
RMSA9
info
Attach RMS Objective to M32 x 0.75 Mount M32 x 0.75 RMS (0.800"-36)
M32RMSSb
info
Attach RMS Objective to M32 x 0.75 Mount M32 x 0.75 RMS (0.800"-36)
RMSA8
info
Mount RMS Microscope Objective to SLR Camera Using M42 x 1.0 to SLR Bayonet Mount Adapter M42 x 1.0 RMS (0.800"-36)
SM2A32
info
Integrate RMS Objective
into SM2 Lens Tube
SM2 (2.035"-40) RMS (0.800"-36)
  • Thermally insulating adapter. See the Thermal Insulation tab above for more information
  • This brass adapter has a flange to prevent overthreading the adapter or the objective into a microscope nosepiece. Brass is harder than aluminum which reduces thread binding.
Adapter with Internal RMS and Internal Industry-Standard Threads
Item # Typical Application Internal Threads Internal Threads
RMSA11
info
Mount RMS Objective in an
M62 x 0.75 System
M62 x 0.75 RMS (0.800"-36)

Threading Specifications

The following is a general overview of screw threading. For more details regarding specifications and dimensions, please consult the Machinery's Handbook, available for purchase at many bookstores.

Features of a Thread
A thread consists of three repeating features: a crest, flank, and root (see drawing to the right). Except in special cases, threads have symmetrical sides inclined at equal angles when a vertical line is drawn through the center of a crest or root. The distance between corresponding points on adjacent threads is known as the pitch of the thread. The flank angle is defined as the angle the flank makes with a perpendicular ray drawn from the screw axis. Unless otherwise stated, threads have a flank angle of 30°, resulting in a total angle between flanks of 60°. Each feature is shown in the diagram to the right.

The major diameter is taken from the crests of a thread while the minor diameter is taken from the roots. For most screws, crests and roots do not terminate at a sharp point, so crest and root truncation values are included in the definitions of major and minor diameter. The pitch diameter is approximately halfway between the major and minor diameters.

Thread Form
A thread form is a set of rules that define the features' scale relative to one another. Common thread forms include the Unified Screw Thread Form, used in the United States of America and measured in imperial units, and the ISO Metric Screw Thread Form, used in many parts of the world and measured with the International System of Units. There are many thread forms in the Unified screw thread standard designated by either UN, which defines a flat root contour, or UNR, which defines a round root contour. These can be further described by appending more letters. For example, an extremely fine thread with a flat root contour is designated UNEF. Those forms which are not standardized by the Unified screw thread system are designated UNS.

Thread Series
Most screws are identified by their thread series. Thread series are denoted by the major diameter and density of threads. Unified threads specify density in threads per inch, while Metric threads specify the thread pitch. For example, in the Unified nomenclature, a 1/4"-20 cap screw has a 1/4" diameter barrel and the pitch is 20 threads per inch (TPI). In metric nomenclature, an M4 x 0.7 cap screw has a 4 mm barrel and the pitch is 1 thread per 0.7 mm. The term M4 x 0.7 is often shortened to just M4.

Unified Thread Class Tolerancing
Location Loose Optimal Strict
Internal 1B 2B 3B
External 1A 2A 3A
Metric Thread Tolerance Positions
Location Loose Optimal Strict
Internal - G H
External e or f g h
Metric Thread Tolerance Grades
Dimension Location Tolerance Gradesa
Minor Diameter Internal 4, 5, 6, 7, 8
Major Diameter External 4, 6, 8
Pitch Diameter Internal 4, 5, 6, 7, 8
External 3, 4, 5, 6, 7, 8, 9
  • The tolerance becomes looser as the grade increases. The underlined grades are used with normal lengths of thread engagement.

Thread Class
The tolerances and allowances on a thread series are given by a thread class. Unified thread classes are alphanumeric identifiers starting with a number from 1 through 3, where 1 is the loosest tolerance and 3 is the tightest, and either A for external threading or B for internal threading.

Metric threads have a slightly more complex tolerancing method that uses tolerancing grades, designated by a number 3 through 9; and tolerancing positions, which use letters e through h. Grades provide a measure of the tolerance itself: the smaller the number, the tighter the tolerance. Positions denote the distance of the tolerance from the pitch diameter. Uppercase positioning letters indicate internal threads while lowercase positioning letters indicate external threads.

Quoting from the Machinery's Handbook, 29th Edition, p. 1885: "To designate the tolerance class, the grade and position of the pitch diameter is shown first followed by that for the major diameter in the case of the external thread or that for the minor diameter in the case of the internal thread, thus 4g6g for an external thread and 5H6H for an internal thread. If the two grades and positions are identical, it is not necessary to repeat the symbols, thus 4g, alone, stands for 4g4g and 5H, alone, stands for 5H5H."

Thorlabs' SM Series Threads
Threading specifications for our SM threads, utilized in our lens tube and cage system components, are given below so that you can machine mating components to suit your application. Most SM series threads utilize a non-standard Unified thread form, indicated by the letters UNS, with a 30° flank angle and a thread class of 2A and 2B. The exception is our SM30 series thread, which is a Metric thread form with a 30° flank angle and a tolerance of 6H/6g. We also offer products with C-Mount and RMS threads, and the specifications for these threads are given below for reference. Please note that other manufacturers may have different tolerances for C-Mount and RMS threads. For other thread specifications that are not listed here, please contact Tech Support.

SM05 Threading: Ø1/2" Lens Tubes, 16 mm Cage Systems
External Thread, 0.535"-40.0 UNS-2A Internal Thread, 0.535"-40.0 UNS-2B
Max Major Diameter 0.5340" Min Major Diameter 0.5350"
Min Major Diameter 0.5289" Min Pitch Diameter 0.5188"
Max Pitch Diameter 0.5178" Max Pitch Diameter 0.5230"
Min Pitch Diameter 0.5146" Min Minor Diameter (and 83.3% of Thread) 0.508"
Max Minor Diameter 0.5069" Max Minor Diameter (and 64.9% of Thread) 0.514"
RMS Threading: Objective, Scan, and Tube Lenses
External Thread, 0.800"-36.0 UNS-2A Internal Thread, 0.800"-36.0 UNS-2B
Max Major Diameter 0.7989" Min Major Diameter 0.8000"
Min Major Diameter 0.7934" Min Pitch Diameter 0.7820"
Max Pitch Diameter 0.7809" Max Pitch Diameter 0.7866"
Min Pitch Diameter 0.7774" Min Minor Diameter (and 83.3% of Thread) 0.770"
Max Minor Diameter 0.7688" Max Minor Diameter (and 64.9% of Thread) 0.777"
C-Mount Threading: Machine Vision Lenses, CCD/CMOS Cameras
External Thread, 1.000"-32.0 UN-2A Internal Thread, 1.000"-32.0 UN-2B
Max Major Diameter 0.9989" Min Major Diameter 1.0000"
Min Major Diameter 0.9929" Min Pitch Diameter 0.9797"
Max Pitch Diameter 0.9786" Max Pitch Diameter 0.9846"
Min Pitch Diameter 0.9748" Min Minor Diameter (and 83.3% of Thread) 0.966"
Max Minor Diameter 0.9651" Max Minor Diameter (and 64.9% of Thread) 0.974"
SM1 Threading: Ø1" Lens Tubes, 30 mm Cage Systems
External Thread, 1.035"-40.0 UNS-2A Internal Thread, 1.035"-40.0 UNS-2B
Max Major Diameter 1.0339" Min Major Diameter 1.0350"
Min Major Diameter 1.0288" Min Pitch Diameter 1.0188"
Max Pitch Diameter 1.0177" Max Pitch Diameter 1.0234"
Min Pitch Diameter 1.0142" Min Minor Diameter (and 83.3% of Thread) 1.008"
Max Minor Diameter 1.0068" Max Minor Diameter (and 64.9% of Thread) 1.014"
SM30 Threading: Ø30 mm Lens Tubes
External Thread, M30.5 x 0.5 – 6H/6g Internal Thread, M30.5 x 0.5 – 6H/6g
Max Major Diameter 30.480 mm Min Major Diameter 30.500 mm
Min Major Diameter 30.371 mm Min Pitch Diameter 30.175 mm
Max Pitch Diameter 30.155 mm Max Pitch Diameter 30.302 mm
Min Pitch Diameter 30.059 mm Min Minor Diameter (and 83.3% of Thread) 29.959 mm
Max Minor Diameter 29.938 mm Max Minor Diameter (and 64.9% of Thread) 30.094 mm
SM1.5 Threading: Ø1.5" Lens Tubes
External Thread, 1.535"-40 UNS-2A Internal Thread, 1.535"-40 UNS-2B
Max Major Diameter 1.5339" Min Major Diameter 1.535"
Min Major Diameter 1.5288" Min Pitch Diameter 1.5188"
Max Pitch Diameter 1.5177" Max Pitch Diameter 1.5236"
Min Pitch Diameter 1.5140" Min Minor Diameter (and 83.3% of Thread) 1.508"
Max Minor Diameter 1.5068" Max Minor Diameter (and 64.9% of Thread) 1.514"
SM2 Threading: Ø2" Lens Tubes, 60 mm Cage Systems
External Thread, 2.035"-40.0 UNS-2A Internal Thread, 2.035"-40.0 UNS-2B
Max Major Diameter 2.0338" Min Major Diameter 2.0350"
Min Major Diameter 2.0287" Min Pitch Diameter 2.0188"
Max Pitch Diameter 2.0176" Max Pitch Diameter 2.0239"
Min Pitch Diameter 2.0137" Min Minor Diameter (and 83.3% of Thread) 2.008"
Max Minor Diameter 2.0067" Max Minor Diameter (and 64.9% of Thread) 2.014"
SM3 Threading: Ø3" Lens Tubes
External Thread, 3.035"-40.0 UNS-2A Internal Thread, 3.035"-40.0 UNS-2B
Max Major Diameter 3.0337" Min Major Diameter 3.0350"
Min Major Diameter 3.0286" Min Pitch Diameter 3.0188"
Max Pitch Diameter 3.0175" Max Pitch Diameter 3.0242"
Min Pitch Diameter 3.0133" Min Minor Diameter (and 83.3% of Thread) 3.008"
Max Minor Diameter 3.0066" Max Minor Diameter (and 64.9% of Thread) 3.014"
SM4 Threading: Ø4" Lens Tubes
External Thread, 4.035"-40 UNS-2A Internal Thread, 4.035"-40.0 UNS-2B
Max Major Diameter 4.0337" Min Major Diameter 4.0350"
Min Major Diameter 4.0286" Min Pitch Diameter 4.0188"
Max Pitch Diameter 4.0175" Max Pitch Diameter 4.0245"
Min Pitch Diameter 4.0131" Min Minor Diameter (and 83.3% of Thread) 4.008"
Max Minor Diameter 4.0066" Max Minor Diameter (and 64.9% of Thread) 4.014"
Legend
Reflectance Heated SM1 Lens Tube with Aluminum Adapter Reflectance Heated SM1 Lens Tube with Delrin® Adapter
Reflectance Unheated SM1 Lens Tube with Aluminum Adapter Reflectance Unheated SM1 Lens Tube with Delrin® Adapter

Thermal Insulation Experiment

An experiment was conducted to compare the thermal isolation of our thermally insulating adapters (SM1A4TS, SM1A9TS, SM1A3TS, and SM1A10TS) presented at the bottom of this page with that of our traditional aluminum adapters. During the experiment, an aluminum adapter and a thermally isolating black Delrin®* adapter were each used to connect two lens tubes. Then, one of the lens tubes was externally heated to 60 °C using a foil heating element that had been attached to that lens tube’s outer surface.

During the heating process, simultaneous temperature readings were recorded in 30 second intervals for both the heated and unheated lens tube in each system. The measured results are shown in the plot to the right. From the graph, it is clearly evident that there is far less heat transfer when using one of our thermally isolating adapters to connect two lens tubes than exists when using an aluminum adapter.

*Delrin is a registered trademark of DuPont Polymers, Inc.

Selection Guide for Thermally Insulating Adapters
Item # Adapter Profile External Threads Internal Threads
SM1A4TS icon RMS (0.800"-36) SM1 (1.035"-40)
SM1A9TS icon C-Mount (1.00"-32) SM1 (1.035"-40)
SM1A3TS icon SM1 (1.035"-40) RMS (0.800"-36)
SM1A10TS icon SM1 (1.035"-40) C-Mount (1.00"-32)

Posted Comments:
johsieh1  (posted 2014-08-22 13:44:26.63)
Hi, I recently received the objective adapter RMSA3 and tried it on our microscope. It does what it supposed to do, mounting a RMS-treaded objective to a M27-treaded microscope turret. However, as the M27 is wider than RMS in size, the objective will not stop at certain depth but continue to advance (until falling off the tread) inside the turret. The objective could not be locked; it was slightly loose in fitting and would move by touch, which makes the center alignment between objectives impossible. I wonder if you would have any adapter that has a thread-locking function at the M27 side that would only go in at a fixed distance? (e.g. join a flat washer on one side of the adapter) Thank you. Jo Hsieh johsieh1@gmail.com
cdaly  (posted 2014-08-26 09:35:27.0)
Response from Chris at Thorlabs: At the moment, we do not have an M27 to RMS adapter with a shoulder to prevent it from threading too deep, but it is possible to achieve this by using two adapters, SM1A18(M27x0.75 to SM1)and SM1A3(SM1 to RMS).
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Adapters with External RMS (0.800"-36) and Internal Industry-Standard Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM05RMS Support Documentation
SM05RMSAdapter with External RMS Threads and Internal SM05 Threads
$17.94
Today
RMSA2 Support Documentation
RMSA2Customer Inspired! Adapter with External RMS Threads and Internal M25 x 0.75 Threads
$26.73
Today
SM1A4 Support Documentation
SM1A4Adapter with External RMS Threads and Internal SM1 Threads
$26.16
Today
SM1A4TS Support Documentation
SM1A4TSCustomer Inspired! Thermally Insulating Adapter with External RMS Threads and Internal SM1 Threads
$25.92
Today
RMSW26S Support Documentation
RMSW26SNEW!Brass Microscope Adapter with External RMS Threads and Internal W26 x 0.706 Threads
$30.00
Today
RMSA4 Support Documentation
RMSA4Customer Inspired! Adapter with External RMS Threads and Internal M27 x 0.75 Threads
$25.54
Today
SM1BC Support Documentation
SM1BCExtended-Length Adapter with External RMS Threads and Internal SM1 Threads
$46.33
Today
RMSA10 Support Documentation
RMSA10Customer Inspired! Adapter with External RMS Threads and Internal M32 x 0.75 Threads
$26.73
Today
RMSA12 Support Documentation
RMSA12Customer Inspired! Adapter with External RMS Threads and Internal M62 x 0.75 Threads
$30.28
Today
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Adapters with Internal RMS (0.800"-36) and External Industry-Standard Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RMSA1 Support Documentation
RMSA1Customer Inspired! Adapter with External M25 x 0.75 Threads and Internal RMS Threads
$23.04
Today
SM1A3 Support Documentation
SM1A3Adapter with External SM1 Threads and Internal RMS Threads
$19.82
Today
SM1A3TS Support Documentation
SM1A3TSCustomer Inspired! Thermally Insulating Adapter with External SM1 Threads and Internal RMS Threads
$25.92
Today
RMSA3 Support Documentation
RMSA3Customer Inspired! Adapter with External M27 x 0.75 Threads and Internal RMS Threads
$25.54
Today
RMSA9 Support Documentation
RMSA9Customer Inspired! Adapter with External M32 x 0.75 Threads and Internal RMS Threads
$26.73
Today
M32RMSS Support Documentation
M32RMSSCustomer Inspired! Brass Microscope Adapter with External M32 x 0.75 Threads and Internal RMS Threads
$27.81
Today
RMSA8 Support Documentation
RMSA8Customer Inspired! Adapter with External M42 x 1.0 Threads and Internal RMS Threads
$24.23
Today
SM2A32 Support Documentation
SM2A32Adapter with External SM2 Threads and Internal RMS Threads
$30.28
Today
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Adapters with Internal RMS (0.800"-36) and Internal Industry-Standard Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RMSA11 Support Documentation
RMSA11Customer Inspired! Adapter with Internal M62 x 0.75 Threads and Internal RMS Threads
$30.28
Today